There's actually a reason we called this object "trBALL", despite the strange syntax. When developing large VRML worlds, your worlds undoubtedly get very messy and unorganized. This is why it is important to make sure your worlds are organized intelligently from the start. In these tutorials we are using our own version of Hungarian notation -- the object name is in CAPS as a postfix, and an abbreviation of exactly what this object is is a prefix. In this case, "trBALL" means that this is the Transform node for the object BALL.